In many sensor applications the sensing elements are resistors which are influenced by a physical quantity to be measured. In order to produce a reliable and a sensitive sensor output, the sensing elements may be connected in a full bridge configuration or so-called Wheatstone bridge configuration. Such a configuration yields a balanced differential output voltage between two intermediate nodes. This differential output voltage is proportional to a supply or bias voltage being applied to the arrangement of the whole full bridge configuration.
In order to perform a digital signal processing analogue bridge signals being present at the two intermediate nodes can be connected to the inputs of a differential high accuracy Analog-to-Digital Converter (ADC) which converts the differential output voltage being given by the difference between the two analog bridge signals into the digital domain. The performance of an ADC is to a large extent determined by the accuracy of two reference voltage levels. Each reference voltage level can be provided by a reference voltage source.
It is known to derive the two reference voltage levels for the ADC indirectly from the supply voltage by means of an appropriate circuitry, which may comprise e.g. voltage dividers. However, this solution for realizing the reference voltage sources providing the two reference voltage levels has the drawback that it is very difficult to generate low noise and accurate reference voltage levels. Further, a significant fraction of the power consumed by the ADC will be used for the generation of the reference voltage levels. Furthermore, in particular with high frequency noise being present at the supply voltage the frequency bandwidth of the reference voltage levels will be different than the frequency bandwidth of the bridge signals. This means that high frequency noise being present on the supply voltage will not be suppressed due to a phase and/or amplitude difference between signal and reference, but will be converted into the digital domain. This could even result in an unwanted aliasing. High frequency noise can further fold back into the Band of Interest (BOI) of the ADC. Moreover, in particular in case of a comparatively intense noise being present on the supply voltage, a large full signal swing of the differential output voltage must be processed by the ADC, resulting in high linearity requirements of the ADC.
As a consequence of the drawbacks mentioned above, the performance of a known sensor system comprising sensing elements being arranged in a full bridge configuration and an ADC for providing a digital output is deteriorated.